Bruiser set and health regen

If everything else fails, maybe add the healing spell to your arsenal!

They literally can't do this. Tanks with sword and board and global life leech, increased health globe drop, and ailments while using juggernaut already have so much sustain that it gets a bit silly (I can't even remember the last time I died). If I was leeching life off of ailments I would be totally unkillable with poison aura, even vs bosses. Don't forget that while the story mode is made more for single player the endgame is really intended to be played with other people (even if its a little broken like that at the moment), so the ideal scenario would be that you have a melee/tank with you dropping extra health globes, a support casting shields/heals, or just straight up someone with threat to reduce the damage you take overall and helping the sustain you do have work better for you.

Adding ailment life leech would just break already strong classes, and your chosen spec would get totally left in the dust anyway, just sayin

Between Level 55 and 60 you find Katalysators what have +4-5% Spell Lifeleech. Best way to play a Mage is the way of a Battlemage.
One Handed + Katalysator, there you have up to 6 sockets, 4-5% Lifeleech on Katalysator and One Hand Weapon, too. You can use at least 1% Global Lifeleech Gems.

You can use Wrath of Baäpheth, with
Blood Brothers - Modifier (gives you 8% Lifeleech)
(Level 32)
Effect: Grants a life leech buff to yourself and allies.

If that 12% Spell Lifeleech is not enough for you use Global Life eech Gems in your sockets and do passive Skill Life leech
In 2nd Segment there are (Warmonger [Red]) +4% Spell Lifeleech and (Warlock[Blue]) , Ravenous Magic +4% Spell Life Leech.

That are 8% with Wrath of Baäpheth + 8 % with Passive Tree , 16%, 4% on a Katalysator and you have 20% Spell Life Leech, where you can add Global Life Leech Gems too.

That for Equipment level 55-60 (Item level)

You have many Chances to get what you want. And if its Life Leech, Do it! I have a Battlemage 50% Blockchance min. Ailment Stack Build too.
There are some Options if you know what you will do with your character.
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Here is a Starter Build for Melee and Battlemages with good amount of Lifeleech + Pssive Tree
https://wolcengame.com/forum/gameplay/builds-guides/basic-starter-build-req-max-lvl-27-holy-lifeleech-massacre-lifeleech-crit-speed-no-healthproblems/

Best way to play a Mage is the way of a Battlemage.

Yeah....thats the point of playing with a 2h staff? Swap it for 1h + catalyst? Lifelech is pretty basic, got 15% already. Problem was that +ailment dmg passives cut the spell dmg, so you end up with less dmg that could leech life. And +xx to spell dmg doesnt do anything for ailmentdamage, so you end up with equip that supports +element dmg or sth but not inreased damage for spells so again: less dmg that can cause lifeleech. It would be appropriate that e.g. +xx fire dmg to spells would increase burning ailment dmg to some extend....

Bulwark of dawn did the trick for me, because it heals my summons too and seems somewhat overpowered with the "increased healing per tick" mod.